I'm listening to an episode of the Point of Inquiry podcast in which they interview Dr. Darrel Ray, the author of The God Virus: How religion infects our lives and culture. Yet another book to add to my wish list.
I have not read the book, but from the interview I gather that the book explains the metaphor of religion as a virus. An example is that you tend to get "infected" with the same virus as your parents.
Dr. Ray made a statement that I found particularly interesting. We think of terrorist bombers when we talk about suicide in the context of religion. However, Dr. Ray used the term "genetic suicide" to describe the effect that religion has on Catholic priests and nuns. That is, they voluntarily exclude their genes from the next generation, and every generation thereafter.